1. Field of the Invention
The present invention pertains to a conveyor system comprising a row former, an array rake and a palletizing sweep mechanism that are arranged in series and are specifically designed to convey objects having irregular cross section shapes. In particular, the present invention pertains to a conveyor system comprising a novel row former, a novel array rake and a novel sweep mechanism that are all designed to prevent relative movement between objects arranged in rows and then formed in two dimensional arrays of the objects as the objects are moved through the conveyor system, where the objects have triangular shaped cross sections.
2. Description of the Related Art
Conveying systems for conveying objects, for example light-weight blow molded plastic bottles, typically include portions of the conveying system that quickly convey one or more single file streams of the objects from one station of the conveying system to another station, for example from a blow molding station where the plastic bottles are formed to a downstream palletizing station where the blow molded plastic bottles are arranged on pallets. Conveying systems often include infeed conveyors that convey one or more single file streams of the objects to a row former. The row former includes pairs of spaced, parallel arms or bars that define a row forming slot between each pair arms for each stream of objects conveyed by the infeed conveyor. The arms are positioned above the infeed conveyor where the slots between the arms receive a number of objects from the streams of objects conveyed by the infeed conveyor and arrange the numbers of objects in rows. With the desired number of objects filling the slots of the row former, the conveyed streams of objects are held back by gates of the infeed conveyor. The row former, with the arranged rows of objects, then moves in a direction perpendicular to the rows of objects across the infeed conveyor and onto the accumulating table surface. The arms of the row former then stop and move upwardly from the accumulating table surface, leaving the numbers of objects in the first arranged rows on the accumulating table surface.
The row former is then moved in the opposite direction back across the accumulating table surface to its position in line with the infeed conveyor. The row former is then moved downwardly aligning the slots between the pairs of arms of the row former with the streams of objects held back on the infeed conveyor. The gates of the infeed conveyor are opened and the slots between the arms of the row former are again filled with numbers of objects conveyed by the conveyor, upon which the gates of the conveyor are closed. The movement of the row former described above is then repeated, leaving numbers of objects in the second arranged rows on the accumulating table surface. This movement of the row former is repeated in forming two dimensional arrays of the objects on the accumulating table surface.
The accumulating table typically includes an array rake that moves across the surface of the table, engaging with the formed array of objects and pushing the formed array of objects over the table surface in the conveyor path direction toward a palletizer. The array rake is typically an elongated bar that extends across the surface of the accumulating table in a direction perpendicular to the conveyed path direction. The rake is moved by chain conveyors that cause the rake to travel across the accumulator table surface, pushing a formed array of objects before the rake across the table surface. When the rake has completed its movement across the table surface, the chain conveyor then moves the rake through its return cycle beneath the table surface before returning the rake to the accumulator table surface to engage with and push the next array of objects formed on the table surface by the row former. The accumulator rake is often used to move a formed array of objects over the accumulator table surface to a position where a sweep mechanism of a palletizer can be clamped over the formed array of objects.
The sweep mechanism of the palletizer is comprised of four panels arranged in a rectangular configuration that are positioned over the formed array of objects on the accumulating table surface. The four panels are moved downwardly over the array and pivot toward each other to clamp around the array of objects formed on the table surface. The sweep mechanism then moves the formed array of objects over the accumulating table surface as a layer of objects to be stacked on a pallet by a palletizer.
Prior art row formers, accumulating table rakes and sweep mechanisms have worked well in arranging numbers of conveyed objects in rows and then positioning the rows side-by-side in forming two dimensional arrays of the objects, and then sweeping the arrays of objects as layers of objects to be palletized where the objects being formed into the arrays are symmetric about their center vertical axes. Plastic blow molded bottles and other such containers that are symmetric about their center vertical axes are examples of such objects. With each of the individual objects in an arranged row being symmetric about its center vertical axis, it did not matter if the object was rotated or caused to move slightly about its center axis as the row former pushed the rows of objects across the infeed conveyor and onto the row accumulating table surface, or as the arrays of objects were moved across the accumulating table surface by the rake or sweep mechanism because the relative orientations of the objects would remain unchanged. However, difficulties were encountered in arranging rows of objects and in forming the rows of objects into two dimensional arrays of the objects when the shapes of the objects changed from the conventional shape, symmetric about its center axis, to asymmetric shapes, for example a plastic, aluminum or cardboard container having a triangular cross section.
A side view of one example of a container 10 having a triangular cross section is shown in FIG. 1. The container is basically comprised of a hollow triangular body 12 having an enlarged base 14 at its bottom and an enlarged rim 16 around a top opening of the container. In forming rows of these containers 10, single file streams of these containers would be supplied to the slots between the row former arms with the containers of each stream of containers being positioned relative to each other as shown in the schematic representations of the positions of the containers in FIG. 2. FIG. 2 shows the relative positions of the containers in four streams of containers supplied by the infeed conveyor to the four slots of a row former. As seen in FIG. 2, adjacent containers of each of the four rows of containers are rotated 180 degrees relative to each other to maximize the number of containers that can be arranged in each row of the row former. However, although the arrangements of the containers in each row shown in FIG. 2 maximizes the numbers of containers occupying each row of the row former, problems arose when the rows of containers were moved from the row former onto the accumulating table surface of the conveyor system and the arms of the row former were removed from between the rows of the containers.
When the rows of containers formed by the row former and moved to the accumulating table surface in two dimensional arrays such as that shown in FIG. 2 were pushed across the accumulating table surface by the forward arm of the row former, or by subsequent rows of containers formed by the row former, or by the array rake of the accumulating table, the point contact between the apexes 18 of the containers in one row with the side walls 20 of the containers in an adjacent row would cause containers to move away from the relative positions shown in FIG. 2. This was primarily due to the instability caused by the single point contact of the apex 18 of each container in one row pushing against or being pushed by the middle of a side wall 20 of a container in an adjacent row. The single point contact of the apex 18 with the side wall 20 would cause the containers in one row being pushed by the containers in an adjacent row to tend to rotate or move to one side or the other of their apexes as the containers are pushed across the accumulating table surface.
To overcome the problem of movement of the triangular shaped containers relative to each other as an array of the containers is pushed across the accumulating table surface by the row former, by subsequently formed rows of containers or by the accumulating table rake, the inventor of the subject matter of the application created a novel arrangement of the triangular containers. In the novel arrangement, the containers of a two dimensional array are not arranged in rows that extend straight across the array with the side wall and apexes of adjacent containers in each row being positioned in a single vertical plane 22 as shown in FIG. 2, but the containers of each row are arranged in a staggered arrangement shown in FIG. 3. In the staggered arrangement, the apexes 18 of the containers in each row are spaced by a gap 24 from the vertical plane 22 in which the side walls 20 of the container in the row are positioned. The staggered arrangement of containers shown in FIG. 3 provides a more stable two dimensional array of containers than that of the array of FIG. 2. In the staggered array of FIG. 3, the side walls 20 of the containers in each row pushed by an apex 18 of a container in the adjacent row are also contacted at opposite ends of the pushed side walls by the two pushing containers on opposite sides of the pushing container making apex contact. Also, the side wall 20 of each pushing container in one row that pushes against an apex 18 of a pushed container in an adjacent row also pushes against the two pushed containers on opposite sides of the pushed container with which it makes apex contact. Thus, the additional points of contact between the containers in adjacent rows prevents the pushed containers from rotating to either side and provides a more stable two dimensional array of containers pushed across the accumulating table surface that maintains the relative positions of the containers as they are pushed across the table surface.
However, the array arrangement of containers shown in FIG. 3 presents the problem of how to establish the staggered relationship between the containers 10 in each row formed across the array and how to maintain the staggered array of containers as the array is pushed across the accumulating table surface and swept from the table surface as a layer to be stacked on a pallet by a palletizer.
The present invention overcome the instability problem of the two dimensional array of triangular shaped containers shown in FIG. 2 by providing a row former that creates the staggered rows of containers shown in the array of FIG. 3, and an accumulating table array rake and a sweep mechanism that maintain the staggered relationship of the containers in the two dimensional array formed and moved across the accumulating table surface of the conveyor system.
The row former of the present invention is similar to prior art row formers but includes several novel additional features. The pairs of row former arms that define the infeed slots of the row former are spaced apart a distance that is slightly larger than the width dimension of the triangular container 10 measured between the apex 18 and side wall 20 of the container. With this spacing between each pair of row former arms, the side walls of adjacent containers formed in a row between each pair of arms engage against one of the arms of the pair and the apexes of adjacent containers are spaced by the predetermined gap 24 from the other arm of the pair, thereby creating the staggered configuration of the containers in the rows. In addition, angled brackets are positioned at the far ends of the slots between the row former arms opposite the openings of the slots. The angled brackets engage against the side walls of the containers at the far ends of the rows of containers formed in the slots to properly orient the containers at the far ends of the slots. By properly orienting the containers at the far ends of the slots, the brackets also orient the subsequent containers conveyed into the slots in forming the staggered rows of containers. In addition, a row retaining gate is provided on at least one of each of the pairs of row former arms adjacent the slot openings at the near ends of the slots. The gate is opened to provide clear access into the slot for the row of containers conveyed to the row former. When the row retaining gate is closed it is positioned in the slot at an angle corresponding to the angles of the side walls of the containers where the gate engages a side wall of an end container of the formed row at the near end of the slot. The engagement of the angled row retainer gate with the end container side wall retains the end container at the slot opening as well as the other containers of the row formed in the slot maintaining the staggered configuration of the containers in the row and holding the containers in their staggered configuration as the row former is moved from the infeed conveyor to the accumulating table surface.
To maintain the staggered arrangements of the rows of containers in the array after they have been pushed onto the accumulating table surface and the row former has been removed, the accumulating table surface has side guide rails that prevent the staggered rows of containers from spreading out and the forwardmost arm of the row former is provided with a series of spaced protrusions or abutments on a front surface of the arm. The protrusions or abutments are positioned and dimensioned to fill the gaps formed between the side walls and apexes of the containers in the last formed row of the staggered array. As the row former pushes subsequently formed rows of containers in the row former slots across the infeed conveyor and onto the accumulating table surface, the forwardmost arm pushes the previously formed array of containers across the accumulating table surface. The abutments on the forwardmost arm occupy the gaps adjacent the apexes of the last formed row of containers in the array and push the apexes of the containers in the last formed row while the front surface of the forwardmost arm engages against and pushes the side walls of the containers in the last formed row. In this way, the forwardmost row former arm pushes the staggered array of containers across the accumulating table surface while maintaining the staggered arrangement of the containers in the array.
To move the two dimensional staggered array of containers formed by the row former further across the accumulating table surface, a modified array rake is provided. The modified rake is similar to prior art accumulating table rakes except that it is also provided with a series of abutments that project from a front surface of the rake. The abutments are arranged on the rake front surface to coincide with the positions of the gaps adjacent the apexes in the last formed row of containers in the array of containers. Like the abutments on the forwardmost row former arm, the abutments on the array rake occupy the gaps adjacent the apexes of the containers in the last formed row of containers of the array and push against the apexes while the front surface of the rake engages and pushes against the side walls of the containers in the last formed row of the array. In this way, the array rake pushes the staggered array of containers across the surface of the accumulating table while maintaining the staggered arrangement of the containers in the array. The rake also has protruding abutments on its rear surface should it be necessary to move a container array across the accumulating table surface back toward the row former.
To transfer a formed two dimensional staggered array of the containers as a layer onto a pallet of containers, a modified sweep mechanism is also provided. The modified sweep mechanism is similar to prior art sweep mechanisms in that it is basically comprised of front and rear panels and two side panels that pivot downwardly clasping around the four sides of the container array to sweep the array to a palletizer. However, the sweep mechanism of the invention differs from prior art sweep mechanisms in that the front and rear opposed panels of the mechanism that fold down and engage with the forwardmost row of containers and the rearwardmost row of containers in the staggered two dimensional array have abutments that occupy the gaps adjacent the apexes of the containers in the forwardmost and rearwardmost array rows. The abutments on the panels engage with the apexes of the containers in the forwardmost and rearwardmost rows of the array as the opposed surfaces of the front and rear panels engage with the side walls of the containers in the forwardmost and rearwardmost rows of the array. In this way the sweep mechanism maintains the two dimensional array of containers in its staggered configuration as the array is swept as a layer from the accumulating table surface to a pallet being formed with stacks of containers by a palletizer.
With the modifications to the conveyor system described above, the conveyor system of the invention is capable of forming rows of objects having triangular cross sections into two dimensional arrays of the objects and then conveying the two dimensional arrays to a palletizer where the layers of objects can be stacked onto a pallet while maintaining the staggered relationship of the objects throughout the conveyor system.